Nanotube switching effect discovered

MUNICH, Germany  Scientists from the Karlsruhe Institute of Technology (KIT) (Karlsruhe, Germany) have unexpectedly discovered a physical effect that potentially can be used to develop novel electronic components. By means of the effect, the conductance of the nanotubes can be controlled.

The scientist team from the KIT Institute for Nanotechnology (INT) have irradiated nanotubes with electrons, resulting in a conductivity decrease in well defined, very small areas by a factor of 1000. By applying high voltages, the effect could be reversed and the nanotubes became conductive again. "With relatively low effort we can achieve a huge effect which is reversible and reproducible," said INT researcher Ralph Krupke. His colleague Christoph Marquardt believes that the effect could be used to design novel electronic components. "This discovery will have a huge effect on the usage of nanotubes in computer chips," he said.

For the experiment, the scientists build an element similar to a transistor, arranging single nanotubes between electrodes. An oxide layer served as substrate. The scientists could produce very small zones of about 10 nanometers that featured very high resistance.

Krupke called the zones "quantum dots" which currently up to now only be produced and integrated into circuits with very high efforts. The quantum dots can be switched on and off much like normal transistors, but they are much smaller.

The scientists believe the reason for the effect discovered lies in the substrate: A part of the electrons get "stuck" in the oxide layer. Afterwards, these electrons disrupt the current in the nanotubes and create locally insulating zones. By applying high voltages, the electrons are "withdrawn by suction," as the scientist puts it.

The DFG Center for Functional Nanostructures has contributed to the research.